An electroless metal plating method is one of the methods for forming a metal film on a base surface having no electric conductivity and this method generally comprises the so-called activation by causing a noble metal such as palladium to adhere in advance as a catalyst to the base surface, as a pretreatment for electroless plating. Methods comprising the steps of treating with an aqueous hydrochloric acid solution of SnCl2 followed by immersing in an aqueous solution of PdCl2, thereby causing the adsorption of Pd, or supporting Pd on the surface by using a colloidal solution comprising Sn and Pd have been heretofore employed. However, a large number of problems associated with the usage of a highly toxic Sn and complex treatment process are inherent to those methods. Accordingly, a variety of methods using silane coupling agents having a functional group capable of forming a complex with noble metals have recently been suggested as methods for supporting a noble metal such as Pd, which is a catalyst for electroless plating, on the surface (see the patent documents 1-8 listed below). With those of the aforesaid methods in which a plating catalyst fixing agent and a plating catalyst were treated separately, that is, when a coupling agent was caused to be absorbed by the article to be plated and then ions of a noble metal serving as a catalyst were supported, it was sometimes difficult to deposit an adherent uniform plating film on the substrate because the substrate is subjected to surface modification by the coupling agent treatment, or because the noble metal ions could not be effectively supported, depending on the substrate material. Even with the methods using a mixed solution of an aminosilane coupling agent and palladium chloride, for the aforesaid reasons or due to the fact that palladium did not fully demonstrate its catalytic activity, uniform plating could not be conducted depending on materials of plating substrates to be plated and plating conditions.
Patent Document 1: Japanese Patent Publication No. 59-52701B
Patent Document 2: Japanese Patent Publication No. 60-181294A
Patent Document 3: Japanese Patent Publication No. 61-194183A
Patent Document 4: Japanese Patent Publication No. 3-44149A
Patent Document 5: Japanese Patent Publication No. 2002-47573A
Patent Document 6: Japanese Patent Publication No. 2002-161389A
Patent Document 7: Japanese Patent Publication No. 2002-226972A
Patent Document 8: WO01/49898A1